1. Field of the Invention
The present invention relates to a punching apparatus for stamping and a method for producing the same for applying perforating machining to a sheet-shaped workpiece.
2. Description of the Related Art
The punching apparatus for stamping has been hitherto used for defining a plurality of holes through a sheet-shaped workpiece by means of stamping machining. Such a punching apparatus for stamping is constructed as follows. That is, a plurality of lengthy holes 1003 are defined through a metal plate or the like by means of electric discharge machining (see FIG. 14A). The holes are precisely finished by means of wire electric discharge machining to produce a punch holder 1002 (see FIG. 14B).
As shown in FIG. 15, lengthy punch members 1004 having a substantially rectangular cross section are inserted into the holes 1003 which are defined through the punch holder 1002 as described above. Roots of the punch members 1004 are secured to the punch holder 1002 by using, for example, an adhesive.
The punch members 1004 are slidably inserted into lengthy holes 1006 of a stripper 1005 which is provided for the punching apparatus for stamping. Further, the punch members 1004 are inserted into lengthy holes 1008 which are defined through a die 1007.
When a plurality of lengthy holes 1011 are bored through a workpiece 1009 such as a green sheet by using the stamping punching apparatus 1001 constructed as described above, the workpiece 1009 is placed on the die 1007. When the punch members 1004 and the stripper 1005 are moved downwardly, the lower surface of the stripper 1005 firstly abuts against the upper surface of the workpiece 1009. Subsequently, the punch members 1004 are moved downwardly to apply the perforating machining to the workpiece 1009.
However, in the case of the conventional stamping punching apparatus 1001 as described above, it is necessary that the hole 1003 is formed to be slightly larger than the dimension of the punch member 1004 in order to insert the punch member 1004 into the hole 1003. For this reason, a slight gap A is generated between the punch member 1004 and the wall for forming the hole 1003 of the punch holder 1002. Therefore, it is difficult to improve the positional accuracy of the respective punch members 1004.
On the other hand, the holes 1006 defined through the stripper 1005 are also formed to be slightly larger than the rectangular dimension of the punch member 1004. For this reason, a gap B exists between the punch member 1004 and the wall of the hole 1006. As a result, the error in positional accuracy of the punch member 1004 is allowable within a range of the gap B. Therefore, a problem arises in that the positional accuracy and the shape accuracy are lowered for the hole 1011 of the workpiece 1009 subjected to the perforating machining performed by the stamping punching apparatus 1001. Further, any unbalanced load is exerted on the stripper 1005 through which the punch member 1004 is inserted. It is feared that the punch member 1004 and the stripper 1005 may be broken.
The hole 1008 of the die 1007 is formed to be larger than the rectangular dimension of the punch member 1004 so that the punch member 1004 is reliably inserted therethrough even when any error exists in the rectangular dimension of the punch member 1004 or in the position of the punch member 1004 with respect to the punch holder 1002. When the pitch between the punch members 1004 is small, the gap between the hole 1008 and the adjoining hole 1008 is narrow. Therefore, the following problem arises. That is, if there is any difference in size between the gaps C1 and C2 generated between the punch member 1004 and the walls for forming the hole 1008 of the die 1007, any inclination (deformation in the right or left direction in FIG. 15) is caused by the gap A in the non-punched portion D of the workpiece 1009, resulting in defect in shape.
Although the respective punch members 1004 are formed to be lengthy in the vertical direction in FIG. 15, their first ends are merely supported by the punch holder 1002. Therefore, it is feared that the punch member 1004 may be deformed by the load exerted on the punch member 1004 during the stamping, or the punch member 1004 is broken due to the buckling.
When the punch member 1004 is exchanged due to any breakage or the like, it is necessary to perform the operation to scrape the cured adhesive by using a grinder or the like. However, during this operation, when the pitch for the punch members 1004 is small, for example, when the punch members 1004 are arranged at a pitch of not more than 0.6 mm, then the following inconvenience appears. That is, for example, a highly sophisticated technique is required for the operation to detach and attach only the punch member 1004 which is required to be exchanged. Further, it is complicated to perform the operation to insert all of the punch members 1004 into the holes 1006 of the stripper 1005 again.
The present invention has been made in order to dissolve the various problems described above, an object of which is to provide a punching apparatus for stamping and a method for producing the same in which the positional accuracy and the shape accuracy of the hole defined through a workpiece are improved by improving the positional accuracy of a punch member, the rigidity of the punch member can be improved, a stripper is prevented from application of any unbalanced load, and the punch member can be easily exchanged.
According to the present invention, there is provided a punching apparatus for stamping for applying perforating machining to a workpiece by using punch members, the apparatus comprising a punch holder secured to an upper die; a die member secured to a lower die; a plurality of grip members detachably fastened to the punch holder; and the plurality of punch members formed on each of the plurality of grip members.
Accordingly, it is unnecessary to individually assemble the punch members to the punch holder one by one, and hence there is no assembling error. Therefore, the positional accuracy of the punch member is improved, and the positional accuracy and the shape accuracy can be improved for the hole to be defined through the workpiece. Further, for example, even when the punch member has a slender pin-shaped configuration, it is possible to reduce the occurrence of fracture and breakage, because its rigidity is enhanced, which is preferred.
It is preferable for the punching apparatus for stamping according to the present invention that the grip member and the punch members are formed in an integrated manner by using a single material.
Accordingly, it is unnecessary to separately produce the grip member and the punch members so that they are assembled to one another. Therefore, the production steps are simplified, and any defect does not occur in positional accuracy of the punch member upon assembling. It is possible to further enhance the rigidity of the punch member.
It is preferable for the punching apparatus for stamping according to the present invention that the grip member has a rectangular cross section, and a plurality of grooves are formed on at least two opposing side walls of the rectangular cross section; and the punch holder is defined with a hole having a rectangular cross section corresponding to the grip member, and the grip member is fitted to the punch holder with a gap such that crosspieces formed between the grooves on the side walls of the grip member slidably contact with side walls of the hole of the punch holder. In this arrangement, it is more preferable that the crosspiece on the side wall of the grip member is formed to have a circular arc-shaped configuration. It is also preferable that the crosspiece involves a circular arc-shaped configuration with its top formed to be flat.
Accordingly, when the grip member integrally provided with the punch members is fitted to the hole of the punch holder, a large amount of adhesive can be contained in the gap between joining surfaces. The expanding effect of the adhesive is also exerted after the joining, because the joining surfaces of the grip member have a large areal size. Thus, it is possible to enhance the adhesive force between the grip member and the punch holder. The adhering performance is excellent as compared with the case in which a flat surface of a grip member is mutually joined to a flat surface of a punch holder.
In the punching apparatus for stamping according to the present invention for applying the perforating processing to the workpiece by using the punch members, it is preferable that the grip member is formed by being divided into two or more holding members, a plurality of grooves having a triangular cross section are formed on a joining surface of one holding member of the two holding members to be joined at a dividing surface, and a joining surface of the other holding member is formed to be flat; each of the punch members is formed to have a pin-shaped configuration; and first ends of the plurality of punch members are inserted into holes defined at the dividing surface.
Accordingly, the grip members and the punch members can be easily formed at a high degree of accuracy in an individual manner.
According to another aspect of the present invention, there is provided a method for producing a punching apparatus for stamping, the method being preferably used and comprising the steps of using a prism-shaped block as a material for the grip member and the punch members; machining a plurality of parallel long grooves separated from each other by arbitrary spacing distances on two opposing side walls of the prism-shaped block; machining tops of crosspieces formed between the long grooves to have a circular arc-shaped configuration; machining long grooves having an arbitrary depth on another side wall so that the long grooves communicate with the long grooves on the two side walls; simultaneously forming thereby the grip member including the plurality of long grooves and the circular arc-shaped crosspieces formed between the long grooves provided on the two opposing side walls and the plurality of punch members each having a lengthy rectangular cross section with its both ends provided with circular arc-shaped portions; and defining a plurality of holes each having a rectangular cross section on the punch holder on the other hand; wherein the grip member is fitted to the punch holder with a gap such that the crosspieces formed on the side walls of the grip member slidably contact with side walls of the hole of the punch holder.
In this arrangement, it is also preferable that the circular arc-shaped top of the crosspiece formed on the side wall of the grip member and the circular arc-shaped portion at the both ends of the punch member are deformed to include flat portions. It is also allowable to omit the step of machining and forming the plurality of parallel long grooves on the side walls of the prism-shaped block by machining and forming the plurality of parallel circular arc-shaped crosspieces on the side walls of the prism-shaped block (see FIG. 7B).
Accordingly, it is possible to further simplify the operation steps for integrally producing the grip members and the punch members, which is preferred.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.